That's exactly what i do with duck, roast first then have chinese lemon duck next! It makes me feel like a king.
I find Gordon Ramsay's roasting method's good:
Mix a couple of tablespoons or five spice with the zest of 2 lemons & an orange and s&p. Score the fat of the duck all over (not so deep you hit the meat) and rub the mix in. Leaving it for a while if you can obviously helps the flavour. Shove the fruit and maybe some star anise, cinnamon or cloves up it's bum.
Now roast as normal but pour honey/golden syrup over it half an hour before it's done.
Rest for 20 mins and then carve some mouth watering duck! Collect the fat that's dripped into the roasting tin, filter/strain it and keep for something else.